(1) Develop a conceptual model of the determinants of pregnancy avoidance behavior, which incorporate fertility awareness and coital behavior factors. This model expands upon the sociological individual- level model of fertility regulation by explicitly including perceptions of pregnancy risk, coital behavior and frequency, and their joint effects of individual actions to avoid or reduce the risk of conception at a given moment in time. (2) Collect three panels of data on the pregnancy avoidance behaviors reported by 900 rural married women between ages 20 to 39 in Sri Lanka on a daily basis for six-week periods. (3) Study and model the covariation between the three behavioral components of the model to understand the relative contribution of each as pregnancy avoiding behavior. (4) Investigate the temporal patterns in each behavior across varying units of time(day/week/month) and within menstrual cycles. (5) compare the measurement of the components of contraceptive prevalence rates obtained with these panel data to that from cross-sectional surveys as to the likelihood of over-or under-estimation. Implementation of the project will lead to a better measurement and ultimately understanding to the determinants of fertility regulation, including the use of medical and non-medical contraception. It will inform and hopefully provide guidelines to existing approaches to estimating contraceptive prevalence in a population used in cross- sectional national probability sample surveys.